Boiling cooler

ABSTRACT

A boiling cooler includes a refrigerant vessel for reserving refrigerant and a heat radiation unit. A heat-generating member is attached to an outer surface of one of two opposite walls of the refrigerant vessel. The heat radiation unit is mounted at an outer surface of other of the walls. A first wick arranged at an inner surface of the one of the walls extends from a lower portion of the wall to an arrangement position of the heat-generating member when the walls are vertically positioned. Refrigerant boiled and vaporized by the heat-generating member enters the heat radiation unit to be condensed and liquidated, then returning to the refrigerant vessel. The heat-generating member can be effectively cooled regardless of the position of the heat-generating member with respect to the refrigerant vessel, in the cases where the refrigerant vessel is used in the vertical direction and in a horizontal direction.

FIELD OF THE INVENTION

The present invention relates to a boiling cooler for cooling a heat-generating member (e.g., semiconductor device) by a latent heat transition due to boiling and condensing of refrigerant.

BACKGROUND OF THE INVENTION

In general, a boiling cooler having a flat shape is arranged horizontally, for example, referring to JP-2002-206880A. The boiling cooler includes a refrigerant vessel (i.e., refrigerant container in JP-2002-206880A) for reserving refrigerant therein, and a heat radiation unit (i.e., radiator in JP-2002-206880A) which is mounted at the upper side of the refrigerant vessel. A heat-generating member (e.g., semiconductor device) is disposed at the lower side of the refrigerant vessel.

The heat radiation unit is provided with two headers which are vertically arranged at the upper side of the refrigerant vessel, and tubes which communicates with the refrigerant vessel through the headers. The tubes are inclined with respect to the refrigerant vessel.

In the boiling cooler, refrigerant in the refrigerant vessel is heated by the heat-generating member to be boiled and vaporized, thus rising to enter the tubes. Then, refrigerant flowing in the tubes is heat-exchanged with outer air to be condensed. Thereafter, refrigerant having been condensed returns to the refrigerant vessel. Thus, heat generated by the heat-generating member is transferred to refrigerant and radiated to outer air in the heat radiation unit, so that the heat-generating member is cooled.

In this case, refrigerant condensed in the tubes flows smoothly because of an incline of the tubes, thus restricting a retention of condensed refrigerant in the tubes and improving a refrigerant cycle performance.

However, recently, it is also required that the above-described boiling cooler can be used in the case where the refrigerant vessel is disposed in a vertical direction, considering a common use by various kinds of electronic devices and an improvement of a packing density of the heat-generating member.

As shown in FIG. 11, in the case where the refrigerant vessel 110 is arranged vertically and the heat-generating member 10 is disposed at the upper portion of the refrigerant vessel 110, it is necessary to increase the liquid surface of refrigerant to correspond to the arrangement position of the heat-generating member 10. Therefore, the effective space (condensation field) in the heat radiation unit 120 is decreased, so that the performance is considerably impaired.

SUMMARY OF THE INVENTION

In view of the above-described disadvantages, it is an object of the present invention to provide a boiling cooler with a high performance for cooling a heat-generating member regardless of a position of the heat-generating member with respect to a refrigerant vessel, in the cases where the refrigerant vessel is positioned in a horizontal direction and in a vertical direction.

According to the present invention, a boiling cooler includes a refrigerant vessel for reserving refrigerant therein, and a heat radiation unit, into which refrigerant boiled and vaporized by a heat-generating member flows to be condensed and liquidized and then returns to the refrigerant vessel. The refrigerant vessel has two opposite walls. The heat-generating member is attached to an outer surface of one of the walls. The heat radiation unit is arranged at an outer surface of other of the walls. A first wick, being arranged at an inner surface of the one of the walls, extends from a lower portion of the wall to a part thereof corresponding to an arrangement position of the heat-generating member when the walls are used to be positioned in a vertical direction.

Therefore, when the boiling cooler is used in the case where the walls are positioned in the vertical direction, refrigerant can be provided for the part corresponding to the arrangement position of the heat-generating member along the inner surface of the one of the walls by the capillary force of the first wick regardless of the position of the heat-generating member even when the liquid surface of refrigerant in the refrigerant vessel is set low. Because the refrigerant liquid surface becomes low, the refrigerant condensation field in the heat radiation unit can be enlarged. Thus, refrigerant boiled and vaporized in the refrigerant vessel is sufficiently condensed and liquefied in the heat radiation unit to radiate a condensation latent heat to the atmosphere. Thereafter, refrigerant returns to the refrigerant vessel to cool the heat-generating member.

Moreover, when the boiling cooler is used in the case where the walls are positioned in a horizontal direction and the heat-generating member is disposed at the lower side of the refrigerant vessel, refrigerant is reserved on the one of the walls. Therefore, refrigerant is readily boiled and vaporized, then sufficiently condensed and liquefied in the heat radiation unit.

Accordingly, the boiling cooler can cool the heat-generating member with a high performance regardless of the position of the heat-generating member with respect to the refrigerant vessel, in the cases where the refrigerant vessel is arranged in both the horizontal direction and the vertical direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a boiling cooler which is used in the case where a refrigerant vessel is positioned in a vertical direction according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing the boiling cooler which is used in the case where the refrigerant vessel is positioned in a horizontal direction according to the first embodiment;

FIG. 3 is a cross-sectional view showing a boiling cooler of Modification 1 according to the first embodiment;

FIG. 4 is a cross-sectional view showing a boiling cooler which is used in the case where a refrigerant vessel is positioned in a vertical direction according to a second embodiment of the present invention;

FIG. 5 is a cross-sectional view showing a head difference of refrigerant liquid in the boiling cooler;

FIG. 6 is a cross-sectional view showing a boiling cooler of Modification 2 according to the second embodiment;

FIG. 7 is a cross-sectional view showing a boiling cooler of Modification 3 according to the second embodiment;

FIG. 8 is a cross-sectional view showing a boiling cooler which is used in the case where a refrigerant vessel is positioned in a vertical direction according to a third embodiment of the present invention;

FIG. 9 is a cross-sectional view showing a boiling cooler which is used in the case where a refrigerant vessel is positioned in a horizontal direction and a heat-generating member is disposed at an upper side of the boiling cooler according to a fourth embodiment of the present invention;

FIG. 10 is a cross-sectional view showing a boiling cooler of Modification 4 according to the fourth embodiment; and

FIG. 11 is a cross-sectional view showing a boiling cooler which is used in the case where a refrigerant vessel is positioned in a vertical direction according to a related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows a boiling cooler 100 which is positioned so that a refrigerant vessel 110 is in an up-down direction (called vertical direction later). FIG. 2 shows this boiling cooler 100 which is positioned so that the refrigerant vessel 110 is in a horizontal direction.

The boiling cooler 100 for cooling a heat-generating member 10 (e.g., semiconductor device) is provided with the refrigerant vessel 110 and a heat radiation unit 120. The components of the boiling cooler 100 are made of, for example, copper or copper base material, and integrally brazed by brazing material which is applied to joint parts of the components.

The refrigerant vessel 110, being a flat box-shaped container, includes a heat reception wall 111 (corresponding to one wall) and a heat radiation wall 112 (corresponding to other wall) which face each other. As shown in FIG. 1, the heat-generating member 10 is fixed to the upper portion of the outer surface of the heat reception wall 111 by fastening units, for example, bolts (not shown), when the boiling cooler 100 is used in the case where the heat reception wall 111 and the heat radiation wall 112 are disposed in the vertical direction. A heat-conductive grease can be also applied between the heat-generating member 10 and the heat reception wall 111 to reduce the contact heat resistance therebetween.

The heat radiation unit 120 includes two headers 121, 122, multiple heat radiation tubes 123 a (or at least one heat radiation tube 123 a), and heat radiation fins 124, each of which is arranged between the adjacent tubes 123 a. The heat radiation tubes 123 a communicate with the headers 121, 122. The headers 121 and 122 are mounted at the outer surface of the heat radiation wall 112, and respectively disposed at the two end sides (upper side and lower side in FIG. 1) of the refrigerant vessel 110. The header 121 (122) is substantially perpendicular to the heat radiation wall 112, and communicates with the refrigerant vessel 110 at an end thereof. The heat radiation tubes 123 a, being substantially parallel to the heat radiation wall 112 (heat reception wall 111), are arranged between the headers 121 and 122 and communicate with the refrigerant vessel 110 through the headers 121 and 122. The heat radiation fin 124, being a corrugate fin, is provided to increase the heat radiation area of the heat radiation unit 120.

As a characteristic part of the present invention, a wick 131 (first wick) is disposed at the inner surface of the heat reception wall 111 of the refrigerant vessel 110, and extends from the lower portion of the heat reception wall 111 (refrigerant vessel 110) to the part thereof corresponding to the arrangement position of the heat-generating member 10. The wick 131 is a porous member made of, for example, a metal net, a metal felt, or a sintered metal. In this embodiment, the wick 131 is made of the sintered metal of copper.

Refrigerant (e.g., water) with a predetermined amount is sealed in the boiling cooler 100, which is vacuumized. The predetermined amount of refrigerant is smaller than or equal to the capacity of the refrigerant vessel 110. Because the boiling cooler 100 is vacummized, the boiling point of water in the boiling cooler 100 becomes 30° C.-40° C. while it is generally 100° C. at the standard atmosphere. Alcohol, fluorocarbon, Freon or the like can be also used as refrigerant besides water.

Next, the operation and the effect of the boiling cooler 100 having the above-described construction will be described.

When the boiling cooler 100 is used in the case where the heat reception wall 111 and the heat radiation wall 112 of the refrigerant vessel 110 are positioned in the vertical direction (referring to FIG. 1), refrigerant in the boiling cooler 100 is reserved in the header 122, and the lower portions of the heat radiation tubes 123 a and the refrigerant vessel 110. The liquid surface of refrigerant in the boiling cooler 100 is lower than the arrangement position of the heat-generating member 10. In this case, refrigerant is drawn upward by a capillary force of the wick 131, thus provided for the part corresponding to the arrangement position of the heat-generating member 10.

Thus, refrigerant absorbs heat from the heat-generating member 10, to be boiled and vaporized. Then, vaporized refrigerant rises in the refrigerant vessel 110, to enter the header 121 and be decentralized into the heat radiation tubes 123 a, as indicated by the broken lines in FIG. 1. Then, refrigerant steam flows in the heat radiation tube 123 a, to be cooled by, for example, cooling air from an air-blowing unit (not shown) to become condensed liquid refrigerant. Condensed liquid refrigerant flows into the header 122 and returns to the refrigerant vessel 110 as indicated by the solid lines in FIG. 1.

Thus, heat generated by the heat-generating member 10 is transferred to refrigerant, through which heat is radiated in the heat radiation unit 120. In the heat radiation unit 120, refrigerant steam is condensed to radiate the condensation latent heat to outer air (cooling air) through the heat radiation fins 124. That is, heat generated by the heat-generating member 10 is transferred to refrigerant and radiated to outer air at the heat radiation unit 120, so that the heat-generating member 10 is cooled.

According to the present invention, when the boiling cooler 100 is used in the case where the walls 111 and 112 are positioned in the vertical direction, refrigerant can be provided for the heat-generating member 10 along the inner surface of the heat reception wall 111 due to the capillary force of the wick 131 even if the liquid surface of refrigerant in the refrigerant vessel 110 is lower than the heat-generating member 10. Because the liquid surface of refrigerant is lower than the heat-generating member 10, the refrigerant condensation field in the heat radiation unit 120 becomes larger, as compared with the related art shown in FIG. 11. Refrigerant is boiled and vaporized in the refrigerant vessel 110. Then, vaporized refrigerant can be sufficiently condensed and liquefied in the heat radiation unit 120 to radiate the condensing latent heat to the atmosphere, then returning to the refrigerant vessel 110 to cool the heat-generating member 10.

Referring to FIG. 2, when this boiling cooler 100 is used in the case where the heat reception wall 111 and the heat radiation wall 112 of the refrigerant vessel 110 are positioned in a horizontal direction and the heat radiation unit 120 is positioned at the upper side of the heat reception wall 111 and the heat radiation wall 112, refrigerant is reserved on the heat reception wall 111 in the refrigerant vessel 110. Therefore, refrigerant is readily boiled and vaporized, then sufficiently condensed and liquefied in the heat radiation unit 120.

Accordingly, the boiling cooler 100 can cool the heat-generating member 10 with a high performance regardless of the position of the heat-generating member 10 with respect to the refrigerant vessel 110, in the both cases where the refrigerant vessel 110 is arranged in the horizontal direction and in the vertical direction.

With reference to FIG. 3 which shows the boiling cooler 100 according to Modification 1 of the first embodiment, the heat radiation unit 120 can be also constructed with a communication header 125 and multiple tubes 123 b arranged substantially perpendicularly to the heat radiation wall 112. The each tube 123 b communicates with the refrigerant vessel 110 at one end of the tube 123 b, and communicates with the communication header 125 at the other end thereof. That is, the multiple tubes 123 b communicates with each other through the communication header 125.

Generally, the extending-direction (i.e., up-down direction in FIG. 3) dimension of the wall 111 (112) is set larger than the dimension of the direction (i.e., left-right direction in FIG. 3) perpendicular to the extending direction thereof. Because the multiple heat radiation tubes 123 b are arranged with respect to the up-down direction, the cross section area of the refrigerant flow passage is enlarged. Thus, the refrigerant flow resistance of the heat radiation unit 120 can be reduced. Therefore, the refrigerant cycle is improved and the cooling performance is bettered.

Second Embodiment

A second embodiment of the present invention is described with reference to FIGS. 4 and 5. In this case, the boiling cooler 100 described in the above first embodiment (referring to FIG. 1) is further provided with a wick 132 (second wick).

According to the second embodiment, referring to FIG. 4, the wick 132 is arranged at the lower portion of the refrigerant vessel 110, when the boiling cooler 100 is used in the case where the walls 111 and 112 are positioned in the vertical direction. The wick 132 is a porous member which is coarser than that of the wick 131. That is, holes formed in the wick 132 are bigger than those in the wick 131.

In the boiling cooler 100, the boiling of refrigerant is developed while the heat-generating member 10 generates heat, so that the refrigerant cycle amount is enlarged. Thus, the refrigerant flow resistance of the heat radiation tubes 123 a is increased (that is, refrigerant pressure loss is increased). As shown in FIG. 5, the pressure PB of vaporized refrigerant at the B point in the heat radiation tube 123 a will become lower than the pressure PA of vaporized refrigerant at the A point in the refrigerant vessel 110 (that is, pressure PA>pressure PB), thus causing a head difference h of the refrigerant liquid. That is, the refrigerant condensation field in the heat radiation unit 120 is decreased.

According to the second embodiment, refrigerant at the side of the heat radiation unit 120 can be drawn to the side of the refrigerant vessel 110 by the capillary force of the wick 132. Therefore, the refrigerant liquid surface in the heat radiation unit 120 is decreased, so that the refrigerant condensation field therein is enlarged. Accordingly, the cooling performance of the boiling cooler 100 is improved.

In this case, it is enough for the wick 132 to be capable of providing the capillary force for drawing refrigerant at the side of the heat radiation unit 120 to the side of the refrigerant vessel 110. Therefore, it is unnecessary for the wick 132 to provide a larger capillary force than the wick 131. Thus, the wick 132 can be constructed of the porous material which is coarser than that of the wick 131. Accordingly, the refrigerant flow resistance of the wick 132 can be reduced, thus smoothing the refrigerant cycle and improving the cooling performance of the boiling cooler 100.

FIG. 6 shows the boiling cooler 100 of Modification 2 according to the second embodiment (referring to FIG. 4). In this case, the wicks 132 and 131 can be also integrally formed by, for example, sintering. As described above, the wick 132 is constructed of the coarser porous material than the wick 131. Thus, the boiling cooler 100 can be constructed with fewer components to be readily assembled, thus reducing the cost.

FIG. 7 shows the boiling cooler 100 of Modification 2 according to the second embodiment (referring to FIG. 4). In this case, the wick 132 can also extend to the part of the heat reception wall 111 corresponding to the arrangement position of the heat-generating member 10. Accordingly, refrigerant can be provided for the heat-generating member 10 through both the wicks 131 and 132, so that the boiling of refrigerant is improved and the refrigerant cycle amount is increased. Thus, the cooling performance is bettered.

Third Embodiment

According to a third embodiment of the present invention with reference to FIG. 8, a partition wall 113 is provided to decrease the head difference h of the refrigerant liquid referring to what is described in the above second embodiment.

In this case, the partition wall 113, through which the wick 131 penetrates, is arranged at the upper side of the refrigerant liquid surface in the refrigerant vessel 110 to partition the interior of the refrigerant vessel 110 into the upper part and the lower part, when the boiling cooler 100 is used in the case where the walls 111 and 112 are positioned in the vertical direction.

Thus, the pressure PA of boiled refrigerant in the refrigerant vessel 110 is not applied to liquid refrigerant in the refrigerant vessel 110, so that the refrigerant liquid surface in the heat radiation unit 120 (heat radiation tube 123 a) can be restricted from getting high. Therefore, the refrigerant condensation field in the heat radiation unit 120 can be enlarged, thus improving the cooling performance.

Fourth Embodiment

A fourth embodiment of the present invention is described with reference to FIG. 9. In this case, the heat-generating member 10 can be cooled even when the boiling cooler 100 (referring to FIG. 1) is used at a position different from that in the above-described first, second and third embodiments.

In this case, a wick 133 (third wick) is arranged in the header 122, and extends from the end (at opposite side to refrigerant vessel 110) of the header 122 to the wick 131.

In this embodiment, the boiling cooler 100 is used in the case where the refrigerant vessel 110 is positioned in the horizontal direction and the heat-generating member 10 is disposed at the upper side of the refrigerant vessel 110. Refrigerant reserved in the lower portion of the heat radiation unit 120 is provided for the heat-generating member 10 by the capillary force of the wick 133 through the wick 131, so that the heat-generating member 10 can be cooled.

FIG. 10 shows the boiling cooler 100 of Modification 4 according to the fourth embodiment. In this case, the heat radiation unit 120 includes the multiple heat radiation tubes 123 b and the communication header 125. A wick 134 (fourth wick) is arranged in one of the tubes 123 b (e.g., right side tube 123 b as indicated in FIG. 10), and extends from the communication header 125 to the wick 131. Thus, the modification of the boiling cooler 100 can have the same effect with that described in this embodiment. 

1. A boiling cooler comprising: a refrigerant vessel, in which refrigerant is reserved, the refrigerant vessel having two opposite walls, a heat-generating member being attached to an outer surface of one of the walls; and a heat radiation unit, into which refrigerant boiled and vaporized by the heat-generating member flows to be condensed and liquidized and then returns to the refrigerant vessel, the heat radiation unit being arranged at an outer surface of other of the walls, characterized by comprising a first wick arranged at an inner surface of the one of the walls, the first wick extending from a lower portion of the wall to a part thereof corresponding to an arrangement position of the heat-generating member when the walls are used to be positioned in an up-down direction.
 2. The boiling cooler according to claim 1, characterized in that the heat radiation unit includes a pair of headers and at least one tube, each of the headers being arranged substantially perpendicularly to the other of the walls and communicating with the refrigerant vessel at one end of the header, the tube being arranged between the headers to be substantially parallel to the walls and communicating with the headers.
 3. The boiling cooler according to claim 1, characterized in that the heat radiation unit includes a plurality of tubes and a communication header, each of the tubes being arranged substantially perpendicularly to the other of the walls and communicating with the refrigerant vessel at one end of the tube, the communication header being connected with each of the tubes at other end of the tube so that the tubes communicate with each other.
 4. The boiling cooler according to claim 1, characterized by comprising a second wick, which is arranged at a lower portion of the refrigerant vessel when the walls are used to be positioned in the up-down direction.
 5. The boiling cooler according to claim 4, characterized in that the second wick is constructed of a porous material which is coarser than that of the first wick.
 6. The boiling cooler according to claim 41 characterized in that the first wick and the second wick are integrally formed.
 7. The boiling cooler according to claim 4, characterized in that the second wick extends to the part corresponding to the arrangement position of the heat-generating member.
 8. The boiling cooler according to claim 1, characterized by comprising a partition wall, which is arranged at an upper side of a refrigerant liquid surface in the refrigerant vessel to partition an interior of the refrigerant vessel into an upper part and a lower part when the walls are used to be positioned in the up-down direction, the first wick penetrating the partition wall.
 9. The boiling cooler according to claim 2, characterized by comprising a third wick, which is arranged in one of the headers and extends from an opposite end of the header with respect to the refrigerant vessel to the first wick.
 10. The boiling cooler according to claim 3, characterized by comprising a fourth wick, which is arranged in one of the tubes and extends from a side of the communication header to the first wick. 